Abrasive Flow Machining(AFM)

What is AFM ?

AFM can Polish and deburr parts internally� Through holes � Intersecting holes� Calibrate fuel injection nozzles to a specific flow rate�

A method to radius difficult to reach surfaces like intricate geometries

Produce surface finish (Ra) as good as 0.05 µm, deburr holes as small �as 0.2 mm radius, edges from 0,025 mm to 1,5 mm

Widely used finishing process to finish complicated shapes and profiles�

Why a Smooth Surface ?

• Reduction in Friction� Aerospace

• Torque and Fuel Economy� Engine

• Eliminate imperfection� Medicine

Major Elements

The three major elements of the process are:(a) The Tooling, which confines and directs the abrasive medium

flow to the areas where deburring, radiusing and surface improvements are desired.

(b) The Machine to control the process variables like extrusion pressure, medium flow volume, and flow rate.

(c) The abrasive laden Polymeric Medium whose rheological properties determine the pattern and aggressiveness of the abrasive action. To formulate the AFM medium, the abrasive particles are blended into special viscoelastic polymer, which show change in viscosity when forced to flow through restrictive passages.

Process Input Parameters of AFM

Extrusion Pressure

Number of cycles� Grit composition and Type� Tooling� Fixture design�

Operating range of AFM Easy flowability Better self deformability� Fine abrading capability� Layer thickness of material removed is, order of about 1µm �

to 10 µm Best surface finish that has been achived as 50nm and �

tolerances +/- 0.5 µm

One-Way AFM

One-way flow AFM processing pushes abrasive media through the work piece in only one direction, allowing the media to exit freely from the part.

The advantages of One Way AFM

• Faster cycle processing• Easy clean-up�• Media temperature control generally not required�• Able to process larger parts�• Simpler tooling and part change-over�• Accurately replicates air or liquids natural flow• Does not encapsulate workpart in media�

Two-Way AFM

The typical two-way flow AFM

process uses two vertically opposed cylinders to extrude an abrasive media back and forth through or around passages formed by the workpiece and tooling.

Abrasive action occurs wherever the media enters and passes through the most restrictive passages

Advantages of Two-Way AFM

• Excellent process control� • Good control of radius generation� • Fully automated system capabilities� • Faster setup & quick-change tooling� • Faster change-over of media�

Orbital AFM

• Surface and edge finishing are achieved by rapid, �

low-amplitude, oscillations of the work piece relative to a self-forming elastic plastic abrasive polishing tool.

• The tool is a pad or layer of abrasive-laden elastic �

plastic medium (similar to that used in two way abrasive flow finishing), but typically higher in viscosity and more in elastic.

Figure: While finishing

Figure: Before start of finishing

Application of AFM

• Automotive� • Aerospace� • Medicine� • Dies and Moulds�

AFM in Aerospace Industry

• � Improved surface quality• � Enhanced high cycle fatigue strength• � Optimized combustion and hydraulics• � Increased airflow• � Extended component life

Before After

AFM in Automotive Industry

• Enhanced uniformity and surface quality of finished components

• Increased engine performance� • Increased flow velocity and volume� • Improved fuel economy and reduced emissions�

• Extended work piece life by reducing wear and stress surfaces

Before AfterFigure : Grains in the same direction to increase flow rates

AFM in Dies and mold Industry

• Reduced production costs�• Increased production throughout �• Enhanced surface uniformity, finish and �

cleanliness• Improved die performance and extend life of �

dies and molds

AFM in Medical Industry

• Eliminate the surface �

imperfections where dangerous contaminates can reside

• Improved functionality, �durability and reliability of medical components

• Enhanced uniformity and cleanliness of surfaces,

• Extended component life�

Figure: Medical implant

Summary

• Possible to control and select the intensity and location of �abrasion

• Produces uniform, repeatable and predictable results on an �impressive range of finishing operations.

• Maintain flexibility and jobs which require hours of highly �skilled hand polishing can be processed in a few minutes

• Process used in � aerospace, medical and automobile industries

• Better surface roughness values and tight tolerances. ��

• Disadvantage of this process is low finishing rate • Better performance is achieved if the process is �

monitored online. • Improve surface quality� • Reduction in Friction� • Eliminate imperfection�

Upper Hydraulic Cylinder

Medium Cylinder

Workpiece Fixture

Lower Hydraulic Cylinder

Abrasive Flow Machining : Experimental Setup

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